Ok so, to state what I already know, the article about Entities describes how to upload the photo and download it as the user that uploaded it. When I upload it I set the Avatar URL as the DownloadUrl that i get when the upload finishes. The problem with this is that DownloadUrl expires.
What I need is when I match two players (opponents) I want to grab that other players Avatar photo.
What way can I achieve this, to Upload the photo as User No.1 and Download the photo as User No.2